Variable voltage device



Sept. 22, 1953 J. MONTGOMERY Filed Sept. 26, 1951 INVENTOR Patented Sept. 22, 1953 UNITED STATES PATENT OFFICE (Granted under Title 35, U.v S. Code (1952),

sec. 266) Claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for govern-mental purposes Without the payment of any royalties thereon or therefor.

My invention relates to an improvement in the construction of a variable voltage apparatus and more particularly, to variable voltage apparatus of the dat card resolver type.

Where it is desired that a supply voltage vary as a function of the sine or cosine of an angle of rotation, use is commonly made of an assembly known as a flat card potentiometer resolver which combines the compactness and accuracy necessary for most purposes. The present state of the art does not allow easy ganging of fiat card resolvers into multiple assemblies.

It isan object of the present invention to pr vide a compact and inexpensive voltage variation apparatus employing the flat card resolver principle which is more adaptable to gauging into multiple assemblies than those heretofore in use.

It is a further object of my invention'to show several means of novel card construction which permits such an improvement in construction of the resolver.

The usual flat card resolver is a flat insulating card circumscribed by a Winding to form a vflat surface. The insulation is removed from the surface of the winding to facilitate electrical contact with a brush assembly. In some applications the winding is grounded at its center and a source of electromati-ve force supplied to each half of the winding in such la manner that the potential of the winding varies along its length being maximum from end to end of the winding. As each brush rotates about an axis through the geometric center of the card, its potential will vary sinusoidally. The shaft cannot pass thro-ugh the cardv for ganging. p

In Ianother embodiment of a fiat card potentiometer the center tap of the winding is not used and the sinusoidally varying potential appears at two brushes spaced 180 degrees apart about the geometrical center of the card.

My invention will be better understood from the following description taken in connection with the accompanying drawings and its sco-pe will be pointed out in the appended claims.

In the drawings, Figure 1 illustrates a dual card design of a flat card resolver, Figures 2, 3, 4 and 5 show other card designs. It is intended that the several means of embodying my invention in fiat card resolvers shown here are illustrations of the invention but it is the intent to use any means which will provide a surface having a center hole to permit a through shaft for ganging and to provide a surface having anv aeolotropic resistance characteristic in the region near the brush path of such a degree that there is substantially no variation of resistance in one direction and the fullest degree of resistance variation in a direction at right angles thereto.

It is further contemplated that the card will be varied slightly in shape to compensatev the output for the loading caused by any impedance used as a load.

In the drawing, Figure 1 illustrates a flat card resolver in which the single card is divided into two individual cards. The cards I and 2 are each preferably made of an insulating phenolic material of good electrical and mechanical characteristics, circumscribed by a winding of high resistance wire and arranged so that a fiat circular uninsulated tnack is available for the brushes' to travel over.

Terminals 3: and' 4 are connected together and likewise 5 and 6'. These pairs of terminals are connected to the opposite polarities of a source of electronic-tive force (not shown).

The brushes T, 8;l 9 and I0' which are mounted on spring-like arms II',v I2, I3, and I4, which are in turn mounted 90.V degrees apart on an insulated support carried on the shaft 5 turning' in bearings (not shown), are connected to slip ringsY (not shown) or through pig tails (not shown) tothe external circuit (not shown).

The rotation of the shaft I5 causes relativemotion of the brushes .and card assembly and sinusoidally varying potential appears across the brushes which are degrees apart. Four brushes permit both sine andcosine functions of the shaft I5 rotation angle toy beY available at the same time.

Groundingl of theA center taps of the two cards (not Shown) will permit of having outputs of plus sine, minus sine, plus cosine and minus cosine simultaneously.

By proper construction the card assembly can be made to rotate with the shaft I5 while the brush structure remains fixed.

Referring to Figure 2, a resistance material is used for a card I6 having conductors I'I and I8 across opposite end surfaces and used as terminals. The card has a center hole of convenient shape and large enough to clear a center shaft (not shown). The sides of the card have material equivalent to that removed from the center, added to the sides so as to maintain the potential gradient between the terminals at a uniform degree and at right angles thereto to have essentially no voltage gradient. It is contemplated to slightly Vary the card shape to compensate for circuit loading.

In Figure 3 an alternate embodiment of my invention is illustrated. A potentiometer card I9, shaped as previously described and illustrated in Figure 2 but with the conducting commutator bars 22 placed upon its face or imbedded so as to form a card consisting of alternating layers of resistance material and commutator bars to form a card showing a high degree of aeolotropic resistance.

In Figure 4 another embodiment of my invention is illustrated. An insulating card 23 has a resistance lm 24 and conductors 25 and 2E attached to it to form an aeolotropic resistance.

A preferred design is to place conducting lines or commutator bars 21 across the face of the conducting lm. The effect of the commutator is to increase the degree of aeolotropy of the resistance card and provide a wear resistant contact path. These bars may be applied over the film resistor or under it.

In Figure 5, the commutator bars permit the resistance path to be removed from under the brushes entirely if so desired. The insulating card 28 has the film resistances 29 and 30 applied to it. Conducting strips 3i and 32 form terminals. Conducting commutator bars 33, parallel to terminals 3| and 32, form a wearresistant path for a contacting mechanism. It is expected to use sufficient commutator bars to get the desired resolution.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An aeolotropic resistance card constructed by stacking alternate layers of conducting material and resistance material, having a center hole, having the outside contour shaped to offset the effect of the central hole and further shaped to reduce the: disturbing effect of the loading when used in the assembly of a sine-cosine potentiometer.

2. A potentiometer comprising, two resistance members having fiat faces, said members each consisting of alternate layers of conductor and resistance materials and being constructed with a recess in the inner edge of each, the two members being mounted so that the recesses provide a central opening; a rotatable shaft mounted to pass through said opening with its axis of rotation substantially normal toi the faces of the members; contacts carried by said shaft, said contacts engaging the faces of the members; said members providing anaeolotropic change in electrical resistance as the contacts are rotated to produce a voltage variation representing the sine or cosine function when connected to a source of potential, said members being contoured on the outer edge to compensate any variation in the resistance of the layers resulting from the opening through which the shaft passes.

3. A resolver potentiometer comprising, a. resistance member having planar surfaces and having a central opening passing through those surfaces; a shaft passing through said opening with its axis at right angles to the surface of said resistance member, said resistance member and said shaft being relatively rotatable, contacts slidably engaging said surface of the resistance member and carried by said shaft; said resistance member consisting of a series of side-byside resistance segments characterized by the property that the potential drop between any two y adjacent segments across the said surface is substantially equal, thus compensating for the structual discontinuity produced by the opening for the shaft, for producing, when connected to a source of potential and relatively rotated, an output proportional to a function of the angle of rotation.

4. A resolver potentiometer as claimed in claim 3 in which the contacts comprise a first set of contacts and a second set of contacts related to the first set of contacts as a function of (0314 where 0 is the angle of relative rotation of the contacts and is the angular displacement between the contacts for generating an output proportional to a function of (9141).

5. A potentiometer comprising, two planar resistance cards each having faces and a rst and second edge mounted with their faces in a common plane and with their first edge closely adjacent, said adjacent edges being recessed to provide a central opening, and said second edge being contoured to compensate for said recesses; a rotatable shaft mounted to extend centrally through said opening with its axis perpendicular to the faces of the cards; said resistance cards being made up of stacked alternate layers of conductor and resistance materials; sliding contact members contacting the faces of the resistance cards and carried by the rotatable shaft for producing an output proportional to a function of the angle of rotation when a voltage is applied to the resistance card.

JAMES L. MONTGOMERY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,416,363 Wellings Feb. 25, 1947 2,457,178 Richardson et al. Dec. 28, 1948 2,531,150 Murdick Nov. 21, 1950 2,556,972 Murdick et al June 12, 1951 

